Sintered electrode for cold cathode tube, and cold cathode tube and liquid crystal display device using the sintered electrode

Abstract

This invention provides a sintered electrode for a cold cathode tube in a cylindrical form having a bottom part on one end and an opening part on the other end, characterized in that a lead-in wire is joined integrally to the bottom part and a requirement of d 2 /d 1> 1 is satisfied wherein d 1 represents the density of the sintered electrode; and d 2 represents the density of the lead-in wire. According to the sintered electrode for a cold cathode tube, the bonding strength between the sintered electrode and the lead-in wire is high, and the handleability is good. The main component of the sintered electrode is particularly preferably identical to the main component of the lead-in wire. Enhancing the density of the lead-in wire can contribute to a further improvement, for example, in reliability.

The invention claimed is: 
     
       1. A sintered electrode for a cold cathode tube in a cylindrical form having a bottom part on one end and an opening part on the other end, wherein a lead-in wire is joined integrally to the bottom part; and
 wherein a requirement of d 2 /d 1 >1 is satisfied, wherein d 1  represents a density of the sintered electrode and is in a range of 90% to 96%, and d 2  represents a density of the lead-in wire and is in a range of 92% to 100%; and 
 wherein a joint interface between the sintered electrode and the lead-in wire is a sintered bond. 
 
     
     
       2. The sintered electrode for a cold cathode tube according to  claim 1 , wherein a main component of the sintered electrode is identical to the main component of the lead-in wire. 
     
     
       3. The sintered electrode for a cold cathode tube according to  claim 1 , wherein the sintered electrode is composed mainly of at least one material selected from tungsten, molybdenum, niobium, tantalum, rhenium, and nickel. 
     
     
       4. The sintered electrode for a cold cathode tube according to  claim 1 , wherein an inner face of the sintered electrode has a surface roughness (Sm) of not more than 100 μm. 
     
     
       5. A cold cathode tube comprising:
 a hollow tubular light transparent bulb having a discharge medium sealed therein; 
 a phosphor layer provided on an inner wall face of the tubular light transparent bulb; and 
 a pair of sintered electrodes for a cold cathode tube according to  claim 1  provided at both ends of the tubular light transparent bulb. 
 
     
     
       6. A liquid crystal display device comprising:
 a cold cathode tube according to  claim 5 ; 
 a light guide body disposed in proximity to the cold cathode tube; 
 a reflector disposed on one side of the light guide body; and 
 a liquid crystal display panel disposed on another side of the light guide body. 
 
     
     
       7. The sintered electrode for a cold cathode tube according to  claim 1 , wherein a front end of the lead-in wire does not extend through a bottom part of the sintered electrode.